/*
    * Copyright 2010-2013 smartics, Kronseder & Reiner GmbH
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    *     http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package de.smartics.xml;
  
  import java.io.StringReader;
  import java.util.Iterator;
  import java.util.Stack;
  
  import javax.xml.stream.XMLEventReader;
  import javax.xml.stream.XMLInputFactory;
  import javax.xml.stream.XMLStreamException;
  import javax.xml.stream.events.Attribute;
  import javax.xml.stream.events.Characters;
  import javax.xml.stream.events.StartElement;
  import javax.xml.stream.events.XMLEvent;
  
  import org.apache.commons.lang.StringUtils;
  import org.w3c.dom.Document;
  import org.w3c.dom.Element;
  import org.w3c.dom.Text;
  
  /**
   * Copies XML information read from one source to another.
   *
   * @author <a href="mailto:robert.reiner@smartics.de">Robert Reiner</a>
   * @version $Revision:591 $
   */
  public class DomCopyReader
  {
    // ********************************* Fields *********************************
  
    // --- constants ------------------------------------------------------------
  
    /**
     * The generic identifier (GI) of the artificial element that is added if the
     * fragment is not enclosed in an element.
     * <p>
     * The value of this constant is {@value}.
     */
    private static final String ARTIFICIAL_GI = "root";
  
    /**
     * The artificial start tag with the {@link #ARTIFICIAL_GI}.
     * <p>
     * The value of this constant is {@value}.
     */
    private static final String ARTIFICIAL_START_TAG = '<' + ARTIFICIAL_GI + '>';
  
    /**
     * The artificial end tag with the {@link #ARTIFICIAL_GI}.
     * <p>
     * The value of this constant is {@value}.
     */
    private static final String ARTIFICIAL_END_TAG = "</" + ARTIFICIAL_GI + '>';
  
    // --- members --------------------------------------------------------------
  
    /**
     * The document to create elements for.
     */
    private final Document document;
  
    /**
     * The elements to write to.
     */
    private final Stack<Element> elements = new Stack<Element>();
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Default constructor.
     *
     * @param document the document to create elements for.
     * @param element the element to write to.
     */
    public DomCopyReader(final Document document, final Element element)
    {
      this.document = document;
      elements.push(element);
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
 
   // --- init -----------------------------------------------------------------
 
   // --- get&set --------------------------------------------------------------
 
   // --- business -------------------------------------------------------------
 
   /**
    * Copies the XML fragment to the writer.
    *
    * @param xmlFragment the XML fragment to read and write to the writer.
    * @throws XMLStreamException on any problem reading from the fragment.
    */
   public void copy(final String xmlFragment) throws XMLStreamException
   {
     final XMLInputFactory factory = XMLInputFactory.newInstance();
     final boolean isFragment = isFragment(xmlFragment);
     final XMLEventReader eventReader;
     if (isFragment)
     {
       eventReader =
           factory.createXMLEventReader(new StringReader(ARTIFICIAL_START_TAG
                                                         + xmlFragment
                                                         + ARTIFICIAL_END_TAG));
       boolean run = true;
       while (run && eventReader.hasNext())
       {
         final XMLEvent event = eventReader.nextEvent();
         if (event.getEventType() == XMLEvent.START_ELEMENT)
         {
           run = false;
         }
       }
     }
     else
     {
       eventReader = factory.createXMLEventReader(new StringReader(xmlFragment));
     }
     parse(eventReader);
   }
 
   /**
    * Checks if the given XML fragment is not enclosed within an element.
    *
    * @param xmlFragment the XML fragment to check.
    * @return <code>true</code> if the fragment is not enclosed in an element,
    *         <code>false</code> otherwise.
    */
   private static boolean isFragment(final String xmlFragment)
   {
     return xmlFragment.charAt(0) != '<';
   }
 
   /**
    * Parses the events from the given event reader.
    *
    * @param eventReader the event reader to read the events from.
    * @throws XMLStreamException on any problem reading the events.
    */
   private void parse(final XMLEventReader eventReader)
     throws XMLStreamException
   {
     int level = 0; // NOPMD
     while (eventReader.hasNext())
     {
       final XMLEvent event = eventReader.nextEvent();
       switch (event.getEventType())
       {
         case XMLEvent.START_ELEMENT:
           level++; // NOPMD
           handleStartElement(event);
           break;
         case XMLEvent.END_ELEMENT:
           level--;
           if (level >= 0)
           {
             elements.pop();
           }
           break;
         case XMLEvent.CHARACTERS:
           final Characters chars = event.asCharacters();
           final String content = chars.getData();
           final Text text = document.createTextNode(content);
           elements.peek().appendChild(text);
         default:
           // Just skip...
           break;
       }
     }
   }
 
   /**
    * Handles the start element with all of its attributes.
    *
    * @param event the event required to be a {@link StartElement}.
    * @throws XMLStreamException on any parsing problem.
    */
   @SuppressWarnings("unchecked")
   private void handleStartElement(final XMLEvent event)
     throws XMLStreamException
   {
     final StartElement element = event.asStartElement();
     final String gi = element.getName().getLocalPart();
     final String prefix = element.getName().getPrefix();
 
     final Element currentElement;
     if (StringUtils.isNotBlank(prefix))
     {
       final String uri = element.getNamespaceURI(prefix);
       currentElement = document.createElementNS(uri, prefix + ':' + gi);
     }
     else
     {
       currentElement = document.createElement(gi);
     }
 
     final Element parentElement = elements.peek();
     parentElement.appendChild(currentElement);
     elements.push(currentElement);
 
     for (final Iterator<Attribute> i = element.getAttributes(); i.hasNext();)
     {
       final Attribute attribute = i.next();
       currentElement.setAttribute(attribute.getName().toString(),
           attribute.getValue());
     }
   }
 
   // --- object basics --------------------------------------------------------
 
 }